This invention relates generally to absorbent structures including an impervious backing sheet, a liquid-permeable facing sheet and a batt disposed therebetween. More specifically, the invention relates to a contoured batt, and a method and apparatus for contouring the batt.
Batts for absorbent structures are often manufactured by air-forming a fibrous web on a continuous moving foraminous wire or screen. A fluff forming chamber deposits fibers onto a first surface of the screen or onto a pervious web, such as tissue, carried on this surface of the screen. A vacuum box beneath an opposing surface of the screen creates a pressure drop between the forming chamber and the screen, thereby facilitating the accumulation of fibers on the screen. A scarfing roll can be positioned downstream from the forming chamber to rake or scarf the fibrous web such that a substantially uniform surface is obtained by removing excess or unwanted fibers.
In some applications, it is desirable that batts formed in this manner be contoured such that they are thicker in some portions than in others. For example, it might be desirable to form the batts such that they are thicker in their central portions than in their marginal portions.
One method of forming contoured batts is disclosed in U.S. Pat. No. 3,975,222 to Mesek. According to this method, a transverse contour is provided by superimposing a narrower strip of compacted fibers upon a wider strip, and a longitudinal contour is provided by varying the rate of feed of the strips. However, this method is not without drawbacks, for example because the use of two sources of fibers and the variation of the feed rate can diminish the efficiency of the process.